Swift：在图像上绘制而不更改其大小（纵横比填充） [英] Swift: Draw on image without changing its size (Aspect fill)

问题描述

我有一个简单的视图控制器，其中整个屏幕都是imageView。 imageView的内容模式设置为 UIViewContentMode.scaleAspectFill 。我可以在图片上绘画，但是一旦完成，图像就会水平缩小。这搞乱了图像的质量，我不确定为什么会这样。

I have a simple view controller where the entire screen is an imageView. The imageView has its content mode set to UIViewContentMode.scaleAspectFill. I can draw on the picture, but as soon as I do the image shrinks horizontally. This messing up the quality of the image and I'm not sure exactly why it's happening.

我看着这个问题，但我听不懂唯一的答案。我认为问题出在我的绘画方式上，而rect正在缩小图像。

I looked at this question, but I didn't understand the only answer. I think the issue is with the way I am drawing and that rect is shrinking the image.

class AnnotateViewController: UIViewController {

    @IBOutlet weak var imageView: UIImageView!

    var lastPoint = CGPoint.zero
    var fromPoint = CGPoint()
    var toPoint = CGPoint.zero
    var brushWidth: CGFloat = 5.0
    var opacity: CGFloat = 1.0


     @IBAction func startDrawing(_ sender: Any) {
        self.isDrawing = !self.isDrawing
        if isDrawing {
            self.imageView.isUserInteractionEnabled = true
            showColorButtons()
        }
        else {
            self.imageView.isUserInteractionEnabled = false
            hideColorButtons()
        }
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first {
            lastPoint = touch.preciseLocation(in: self.imageView)
        }
    }

    func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint) {
        UIGraphicsBeginImageContextWithOptions(self.imageView.bounds.size, false, 0.0)
        imageView.image?.draw(in: CGRect(x: 0, y: 0, width: screenSize.width, height: screenSize.height))

        let context = UIGraphicsGetCurrentContext()
        context?.move(to: fromPoint)
        context?.addLine(to: toPoint)


        context?.setLineCap(CGLineCap.round)
        context?.setLineWidth(brushWidth)
        context?.setStrokeColor(red: 255, green: 0, blue: 0, alpha: 1.0)
        context?.setBlendMode(CGBlendMode.normal)
        context?.strokePath()

        imageView.image = UIGraphicsGetImageFromCurrentImageContext()
        imageView.alpha = opacity
        UIGraphicsEndImageContext()

    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first {
            let currentPoint = touch.preciseLocation(in: self.imageView)
            drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint)
            lastPoint = currentPoint
        }
    }
}

更新-解决方案

我终于回到解决该问题的方法了。看着这个问题，我能够使用接受的答案来解决我的问题问题。下面是我的更新代码：

I finally got back to working on this problem. Looking at this question, I was able to use the accepted answer to solve my problem. Below is my updated code:

func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint) {
        UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, true, 0.0)

        let aspect = imageView.image!.size.width / imageView.image!.size.height
        let rect: CGRect
        if imageView.frame.width / aspect > imageView.frame.height {
            let height = imageView.frame.width / aspect
            rect = CGRect(x: 0, y: (imageView.frame.height - height) / 2,
                          width: imageView.frame.width, height: height)
        } else {
            let width = imageView.frame.height * aspect
            rect = CGRect(x: (imageView.frame.width - width) / 2, y: 0,
                          width: width, height: imageView.frame.height)
        }
        imageView.image?.draw(in: rect)

        let context = UIGraphicsGetCurrentContext()
        context?.move(to: fromPoint)
        context?.addLine(to: toPoint)
        context?.setLineCap(CGLineCap.round)
        context?.setLineWidth(brushWidth)
        context?.setStrokeColor(red: self.red, green: self.green, blue: self.blue, alpha: 1.0)
        context?.setBlendMode(CGBlendMode.normal)
        context?.strokePath()

        imageView.image = UIGraphicsGetImageFromCurrentImageContext()
        annotatedImage = imageView.image
        imageView.alpha = opacity
        UIGraphicsEndImageContext()
    }

推荐答案

此行：

imageView.image?.draw(in: CGRect(x: 0, y: 0, width: screenSize.width, height: screenSize.height))

以屏幕的长宽比绘制图像，但是您的图像可能不是相同的宽高比（宽高比）。

Draws the image at the aspect ratio of the screen, but your image is probably not at the same aspect ratio (the ratio of width to height).

我认为这可能会有用： UIImage Aspect Fit当使用drawInRect时？

I think this might be useful: UIImage Aspect Fit when using drawInRect?

这篇关于Swift：在图像上绘制而不更改其大小（纵横比填充）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！